Grandiflora Rose Care Information

Grandiflora roses make excellent cut flowers.

Gardeners who like the size and shape of hybrid tea roses but the clusters of blooms produced by floribunda roses will find the perfect balance of the two in grandiflora roses. Resulting from a cross between hybrid teas and floribundas, grandifloras produce clusters of five to seven large blooms on 3-to-5-foot-long canes. Some varieties may reach 10 feet in height, while retaining their rounded, bush-like habit. Care of these roses is similar to other rose types.

Culture

Grandiflora roses grow in U.S. Department of Agriculture plant hardiness zones 5 through 9. Like other rose varieties, grandifloras grow best in full sunlight conditions, with at least 6 hours of direct, bright sunlight per day. They prefer fast-draining, fertile, loamy soils with a pH near 7.0. Planting grandifloras with a spacing of 6 feet is necessary to provide adequate air circulation and room for future growth.

Water and Fertilizer

Roses require supplemental watering when the top 1 to 2 inches of surrounding soil becomes dry. Applying water directly to the ground, only in the morning hours will reduce the risk of fungal diseases forming on the plant's leaves. Fertilizing grandifloras with a 5-10-5 nitrogen, phosphorous, potassium slow-release fertilizer three times per year will provide adequate nutrients. Space each application six weeks apart, starting with the first in the spring once new growth is 6 inches long. Spread 1 tablespoon of fertilizer around the base of each plant. Mix the fertilizer into the top 3 inches of soil and water the area thoroughly.

Pruning

Yearly pruning is important to a grandflora rose's health and overall shape. Always prune roses in late winter while they are still dormant, just before their buds start swelling. Removal of damaged, broken, diseased or dead canes first will increase the plant's health. Pruning away suckers, weak stems and branches that cross or rub against others will resolve problem areas. Thinning the remaining canes, removing the oldest canes first and leaving three to seven of the healthiest canes, will rejuvenate the plant. Cut the top one-third to one-half off the remaining canes to control height. Ensure proper future growth by making each cut one-quarter inch above an outward facing bud or lateral branch.

Maintenance

Spreading a 1-inch deep layer of mulch around your granidflora rose plant will control weed growth while reducing moisture loss and insulating roots. Periodically checking leaves for signs of disease and insect infestations is important to maintaining plant health. Spraying roses with fungicides in the spring when wet weather persists will provide a defense against fungal diseases. Using insecticidal soaps and horticultural oils on plants infested with aphids, scale and whiteflies will eliminate these pests.